Activation of particulate aluminum

ABSTRACT

Milling of particulate aluminum in the presence of a material capable of sorbing onto the surface of the aluminum sufficiently to stabilize it and at the same time be readily displaceable, thereby producing a reactive or pyrophoric aluminum.

United States Patent [191 Kondis 1 ACTIVATION 0F PARTICULATE ALUMINUM [75] Inventor: Thomas J. Kondis, Pittsburgh, Pa.

[73] Assignee: Aluminum Company of America,

Alcoa Center, Pa.

[22] Filed: Nov. 17, 1972 21 Appl. No.: 307,334

[52] US. Cl 148/627; 75/213; 117/100 M; 117/134 [51] Int. Cl. C23f 7/00 [58] Field of Search 148/627; 241/15; 75/213; 29/4.5 R; 117/100 M, 109, 134; 149/6 [56] References Cited UNITED STATES PATENTS 2,894,864 7/1959 Ek et al. 117/134 X June 17, 1975 3,153,584 10/1964 Goon 117/100 M 3,674,541 7/1972 lchiki et a1 117/62 3,704,176 1l/1972 Oga ct 211. 148/627 3,734,784 5/1973 Bereday ct a1 148/627 3,781,177 12/1973 Kondis ct al. 149/6 Primary Examiner-Thomas .1. Herbert, Jr. Attorney, Agent, or Firm.1ohn P. Taylor, Esq.; Abram W. Hatcher, Esq.

[57] ABSTRACT 16 Claims, No Drawings ACTIVATION OF PARTICULATE ALUMINUM BACKGROUND OF THE INVENTION l. Field of the Invention This invention relates to activation of aluminum particles. More particularly, it relates to a method for producing an active particulate aluminum by improved milling. By aluminum, I mean aluminum and aluminum base alloys containing at least SO 1 by weight aluminum.

2. Description of the Prior Art Particulate aluminum or aluminum powder, for example, atomized powder, is conventionally milled in an inert atmosphere, sometimes in the presence of inert hydrocarbons such as hexane, kerosene. benzene, min eral spirits and the like, to avoid excessive formation of an oxide-coated surface and to produce aluminum which will combine under pressure with hydrogen gas and an olefin such as ethylene or isobutylene to form an alkylaluminum compound. Aluminum milled in this way, however. does not always exhibit the required degree of activity, perhaps because of the formation of conglomerates of small particles welded and pounded together in a manner which prevents formation of the desired amount of fines ofsmall particle size and of sufficient surface area and low oxide content, Therefore, finding a method of insuring production of an active or pyrophoric aluminum consistently sufficiently reactive to form further useful products such as catalytic aluminum alkyls represents a highly desirable resultv SUMMARY OF THE INVENTION After extended investigation I have discovered such a method. I have found that milling particulate aluminum in the presence of a material (which I will call a milling aid) that will sorb onto the surface of the aluminum sufficiently to stabilize it but insufficiently to prevent access to the nascent aluminum surface by a reactive substance imparts to aluminum a high degree of activity, particularly, chemical reactivity. Highly sorptive oxygen-containing compounds of limited reactivity have been found to be most efficient in preparing active aluminum according to the invention. By highly sorptive, I mean having the capability of being easily or readily sorbed onto the surface of the aluminum particles. By of limited reactivity, I mean of insufficient reactivity to react to produce an undesirable new compound in bulk during the milling. The milling aid must be so constructed or made up that it sorbs onto the surface of the particulate aluminum during milling just enough to protect it adequately in the mill, that is, just enough to promote comminution rather than welding of particles, but can be displaced by another material or otherwise allow access to the nascent aluminum after completion of the milling. It should leave sites of nascent aluminum intermingled with sorbed sites.

Preferred compounds coming within this category include ketones, aldehydes, amides. carboxylic acids, peroxides, epoxies, ethers (such as i-propyl ether), esters, organic phosphates, organic nitrates, organic sulfonates, silicones and anhydrides. Olefins. hydrocarbon free radicals, hydrazine free radicals and chlorinated hydrocarbons (including carbon tetrachloride) are also representive of materials which have the required sorptive power, that is, power to be sorbed on the surface of the aluminum, for producing the desired activity in aluminum milled according to the invention.

The particulate aluminum that may be activated in the presence of milling aids such as identified hereinabove includes atomized aluminum, granulated aluminum, powdered aluminum, aluminum powder. or any other type of aluminum particles fine enough to be milled, for example, in a rotating ball mill or vibratory mill, The particle size is not critical according to the in vention. Preferred milling is in the presence of an inert hydrocarbon such as benzene or kerosene in addition to the required milling aid. Milling time is significant only insofar as milling does not continue beyond the time required to generate enough new surface to sorb the milling aid available in the mill, as total utilization of the milling aid causes an active milling environment to revert to an inactive environment, and welding rather than'c'omminution' begins to predominate. Nor

is the temperature during milling critical, room temperature being satisfactory.

Prior to my invention, that is. in the absence of the milling aids defined hereinabove, the fresh surfaces generated on the aluminum during milling were unstable under conventional milling conditions. Thus, the particles were readily combined and/or welded to gether, particularly when ball milled. Nor does the common practice of recycling a portion of the product alkylaluminum compound back to the mill prevent the aluminum particles from re-combining and welding. as trialkylaluminum compounds are not adequately sorbed to the surface sufficiently to promote comminution. According to my invention, on the contrary, milling aids such as those identified and listed hereinabove. effectively stabilize the surfaces freshly generated during ball milling by reacting almost immediately with the virgin aluminum or by sorbing on its surfaces, thereby precluding it from physically contacting other virgin aluminum surfaces.

According to the invention it appears that a mechanism of surface stabilization of the aluminum operates through attack of the surface by the oxygen portions of the organic molecules when oxygen-containing materials are used as the milling aids. While I do not wish to be bound by any particular theory of how this attack may occur, in the case of methyl ethyl ketone, for example, a preferred milling aid according to the invention, the reaction may be postulated as follows, illustrating the carbonyl pi bond as a pair of dots:

cs (3H3 ps c11 cs CH2 l l I 6N0 .Al .C-O-Al C-O-Al a- (surface)! H 011 a-c-a 011 DESCRIPTION OF THE PREFERRED EMBODIMENTS The following examples are illustrative of the invention.

EXAMPLE 1 Two samples of atomized aluminum powder milled under substantially identical conditions in hexane, one

in the presence of milling aid and the other not, were compared to illustrate the improved reactivity brought about by using milling aids according to the invention. The powder milled in the absence of a milling aid (here, methyl ethyl ketone) did not react immediately in 0.7N nitric acid but required several hours for penetration of the acid to the surfaces of the aluminum particles, the reaction even then being very difficult to detect, only a few bubbles of hydrogen being evolved. On the other hand, powder milled in hexane containing 0.0085 mole methyl ethyl ketone (MEK) per mole aluminum when immersed in distilled water, resulted in an immediate reaction between the water and the aluminum particles, visually observed in the generation of hydrogen bubbles at the surfaces. The powder milled in the presence of MEK also reacted vigorously in the 0.7N nitric acid. begining immediately upon contact, thereby confirming the activity created by use of the milling aid, here methyl ethyl ketone.

EXAMPLE 2 The data in the following table (Table I) compares results obtained by use of methyl ethyl ketone milling aid alone and in 0.5% and 3% concentrations in hexane with results obtained by use of the solvent hexane alone without a milling aid in ball milling atomized aluminum powder (Aluminum Association designation 1 100). Degree of activity of the product is indicated by the amount of oxygen consumed in reactivity tests and oxide content. In general, the activated aluminum having the higher surface areas was more active than that having the lower surface areas. Oxygen consumption was determined by removing the liquid carrier from the mill by vacuum distillation after milling. Known amounts of dry oxygen were then metered incrementally into the milling cylinder until no further losses in pressure were noted on a manometer connected into the system. At this point, formation of aluminum oxide was assumed to be complete and oxygen requirements of the activated powder satisfied. The quantity of oxygen thus converted to oxide was calculated as the indicated millimoles oxygen per gram of aluminum. Oxide content was determined quantitatively by weighing the powder sample before and after stripping with a chromic-phosphoric acid solution.

MESH WEIGHT +l 2 0.0 2+40 I 1.8 40+l00 26.6 l+200 I8.6 -200+325 I3.6 -325 29.4

Table I Surface Milling O Consumed Oxide Area Media Run mmoles/g Percent m lg Methyl Ethyl Ketone 7.1 4 0.398 8.7 7.79 Hexane I 0.000 0.3 0.08 2 0.000 0.5 0.10 3 0.000 0.1 0.08 4 0.000 0.3 0.07 3% Methyl Ethyl Ketone in Hexane 5.2 0.5% MEK in Hexane EXAMPLE 3 Table II below shows the surface area of atomized aluminum powder activated by ball milling in several different sorption-susceptible milling aids according to the invention, Indication of the higher reactivity of the aluminum activated by use of milling aids according to the invention was shown by the higher surface area for each than for the control, where a prior art conventional mill additive, stearic acid, was used. Tests were made both under oxygen and in a vacuum. Table II also illustrates use of various solvents in the wet grinding.

Surface area was measured by the conventional BET sorption method, which involves measuring the quantity of krypton gas necessary to produce an adsorbed monolayer over the particle surfaces.

Other milling aids employed successfully according to the invention, but associated with which some exothermal fusion was encountered, included dimethyl formamide, phthalic anhydride and dimethyl phthalate. Epon 826, a bisphenolepichlorohydrin-derived liquid epoxy resin containing primarily ether and epoxide, with perhaps a small amount of hydroxy, functionally,

EXAMPLE 5 Commercial purity atomized aluminum powder was milled in a benzene solution containing 0.04 mole triethylaluminum per mole slurried aluminum, and was subsequently reacted in an autoclave at 120C with 3.2 moles triethylaluminum per mole aluminum under 2000 psi hydrogen gas. Conversion of triethylaluminum to diethylaluminum hydride commenced after an induction period of 44 minutes, as indicated by a decrease in hydrogen pressure, and reaction proceeded thereafter at a constant rate, consuming 5.7 psi hydrogen per minute. A second sample of commercial purity atomized aluminum from the same lot was likewise milled. except that the benzene solution contained 0.01 mole methyl ethyl ketone per mole aluminum in place of the aforementioned 0.04 mole triethylaluminum. The aluminum thus activated was subsequently reacted with 3.2 moles triethylaluminum per mole aluminum as before. Conversion of triethylaluminum to diethylaluminum hydride commenced after only 13 minutes, and reaction proceeded, consuming 1 1.22 psi hydrogen per minute. Thus, a threefold decrease in the length of the induction period. and a twofold increase in reaction rate were realized as a result of activation using methyl ethyl ketone.

EXAMPLE 6 Table Ill shows activation results for use of additional milling aids according to the invention, comparing them with results obtained by using hydrocarbon sol vents alone and with results obtained by using nitrogen pressurized atmospheres during milling.

Table 11! Oxygen Surface Area Carrier Mill Consumption Radiochemical BET Krypton Oxide Milling Aid Liquid Atmosphere mmoles/g m /g m /g Percent none hexane vacuum 0.000 0.08 0.3 none benzene vacuum 0.000 0.04 0.2 none mineral vacuum 0.000 0.07 0.3

spirits none cyclohexane vacuum 0.000 0.10 1.7 aluminum chloride benzene vacuum 0.003 0.8 13.3 dioxane hexane vacuum 0003 0.2 0.2 propyl ether hexane vacuum 0.006 0.1 0.4 triethylaluminum hexane vacuum 0.011 3.2 1.3 tetraphenylhydrazine benzene vacuum 0.017 0.86 1.7 maleic anhydride benzene vacuum 0.029 0.9 0.3 ethylene hexane 200 psi ethylene 0.036 0.57 0.4 2-hexene hexane vacuum 0.044 0.9 0.5 isoprene hexane vacuum 0.048 0.8 0.7 hexaphenylethane benzene vacuum 0.050 0.88 0.7 formamide hexane vacuum 0057 1.0 0.9 stearic acid mineral 15 psi N 0.121 4.23 3.6 4.8

spirits benzoyl peroxide benzene vacuum 0.142 4.68 9.0 none diisobutyl vacuum 0.146 5.19 7.2

ketone propionic acid hexane vacuum 0.160 5.79 7.5 stearic acid mineral vacuum 0.178 3.76 4.6 MEK spirits acetophenone benzene vacuum 0.193 4.28 7 1 t-butyl peroxide hexane vacuum 0.200 221 0.0 none acetone vacuum 0.204 5.45 7.3 MEK benzene vacuum 0.205 4.75 5.3 .9 MEK mineral vacuum 0.208 4.94 5.2 4.6

spirits stearic acid mineral vacuum 0.210 3.77 2.8 4.7

spirits propylene oxide hexane vacuum 0.213 2.6 1.4 MEK mineral 15 psi N 0232 5.63 3.6

spirits benzaldehyde benzene vacuum 0.247 4.79 7.1 l-naphthaldehyde benzene vacuum 0.249 4.61 5.4 cyclohexanone cyclohexane vacuum 0.277 6.45 12.3 Sylkyd 50' benzene vacuum 0.291 4.57 2.8 ethyl acetate hexane vacuum 0.328 7.00 2.2 polyvinyl methyl ether benzene vacuum 0.335 5.52 4.7 octyl diphenyl phoshexane vacuum 0.393 458 2 phate none MEK vacuum 0.395 7.96 7.7 Epon 826 benzene vacuum 0.400 20.8 32 62- acetaldehyde hexane vacuum 0.414 7.86 13.0 benzophenone benzene 200 psi ethylene 0.419 6.6 5.5 propionaldehyde hexane vacuum 0.454 7.33 103 l-nitropropane hexane vacuum 0.472 7 7 3 3 benzophenone benzene vacuum 0.483 7.99 9.6 3.3

Table in Continued Oxygen Surface Area Carrier Mill Consumption Radiochemical BET Krypton Oxide Milling Aid Liquid Atmosphere mmoles/g m /g m lg Percent acetyl acetone hexane vacuum 0.507 I 8 3.2 phthalic anhydride benzene vacuum 0.538 103 1.0 dimethyl phthalate benzene vacuum 0.577 Z-60 l 8' benzene vacuum 0.581 5.78 0.6 MEK hexane 200 psi ethylene 0.626 8.03 l .5 9.6 MEK hexane vacuum 0.659 8.98 7.7 5,2 dimethyl formamide hexane vacuum 0.780 6.7 1,2

'Dil1\Llh)i triphcnyltrimcthoxytrisiloxunc (a silicone intermediate, from Dow Corning) |.iquid epoxy resin. hisphcnol-cpichlorohydrin lyric. Shcll Chcmical "Weight gain uftcr stripping Siliconc intcrmcdiatc. hydrox functional. Dow Corning While the invention has been described in terms of preferred embodiments, the claims appended hereto are intended to encompass all embodiments which fall within the spirit of the invention.

Having thus described my invention and certain preferred embodiments thereof, 1 claim:

1. A process for production of a highly reactive pyrophoric aluminum which permits creation and maintenance of nascent aluminum surfaces while inhibiting rewelding together of such surfaces which comprises milling particulate aluminum in the presence ofa milling aid capable of sorbing onto the surface of the aluminum sufficiently to prevent welding of the particles and at the same time allow access by a reactive substance to the nascent aluminum surface; said milling aid being selected from the group consisting of: oxygencontaining compounds, olefms, hyrocarbon free radicals, hydrazine free radicals, and chlorinated hydrocarbons.

2. The process of claim 1 wherein the particulate aluminum comprises atomized aluminum powder.

3. The process of claim 1 wherein the milling aid is selected from the group consisting of ketones, aldehydes, amides, carboxylic acids, peroxides, epoxies, ethers, esters, organic phosphates, organic nitrates, organic sulfonates, silicones and anhydrides.

4. The process of claim 1 wherein the milling aid is a highly sorptive oxygen-containing compound having insufficient reactivity to react to produce an undesirable compound in bulk during milling.

5. The process of claim 1 wherein the milling is in the presence of an inert hydrocarbon.

6. The process of claim 5 wherein the inert hydrocarbon is selected from the group consisting of hexane kerosene, mineral spirits and benzene.

7. A dispersion adapted for activating particulate aluminum during milling same to permit creation and maintenance of nascent aluminum surfaces while inhibiting welding together of such surfaces, said dispersion comprising:

a. particulate aluminum,

b. a milling aid capable of sorbing onto the surface of the aluminum sufficiently to prevent welding of the particles and at the same time allow assess by a reactive substance to the nascent aluminum surface selected from the group consisting of oxygencontaining compounds, olefins, hydrocarbon free radicals, hydrazine free radicals, and chlorinated hydrocarbons, and

c. an inert hydrocarbon.

8. The dispersion of claim 7 wherein the particulate aluminum comprises atomized aluminum powder.

9. The dispersion of claim 7 wherein the milling aid is selected from the group consisting of ketones, aldehydes, amides, carboxylic acids, peroxides, epoxies, ethers, esters, organic phosphates, organic nitrates, organic sulfonates, silicones and anhydrides.

10. The dispersion of claim 7 wherein the milling aid is a highly sorptive oxygen-containing compound of limited reactivity to stabilize the surface without preventing access to the nascent aluminum after completion of the milling.

11. A process for improving the reactivity of aluminum which comprises milling particles of atomized aluminum in the presence of an inert hydrocarbon and at least one sorptive-type milling aid selected from the group consisting of ketones, amides, aldehydes, carboxylic acids, peroxides, epoxies, esters, organic phosphates, organic nitrates, organic sulfonates, silicones, anhydrides, olefins, hydrocarbon free radicals, hydrazine free radicals, and chlorinated hydrocarbons, thereby sorbing said milling aid on the surface of said particles to promote the reactivity thereof.

12. A process for creating and maintaining nascent surfaces on particulate aluminum which comprises attacking freshly generated nascent surfaces of particles of aluminum with oxygen portions of oxygencontaining organic molecules during milling said aluminum, thereby stabilizing said surfaces to a controlled reactivity sufficient to prevent welding of the particles.

13. The process of claim 12 wherein the surfaces of the particles of aluminum are stabilized sufficiently to make them reactive with hydrogen and an olefin to form an aluminum alkyl compound.

14. A process for activating aluminum powder which comprises milling particulate aluminum in the presence of a milling aid capable of sorbing onto the surface of the aluminum sufficiently to stabilize it and at the same time allow access by a reactive substance to the nascent aluminum surface, said milling aid comprising at least one substance selected from the group consisting of methyl ethyl ketone, benzophenone, dimethyl phthalate, dioctyl phthalate, phthalic anhydride, dioxane, ipropylether, benzoyl peroxide, propylene oxide, benzaldehyde, l-naphthaldehyde, cyclohexanone, tetraphenyl hydrazine, dimethyl triphenyltrimethoxytrisiloxane, bisphenolepichlorohydrin-derived ether-epoxide epoxide resin, ethyl actate, polyvinyl methyl ether, octyl diphenyl phosphate, phthalic anhydride, acetyl acetone, dimethyl formamide, propionaldehyde, 1-

trolled reactivity, said oxygen-containing organic molecules being provided in at least one substance selected from the group consisting of methyl ethyl ketone, benzophenone, dimethyl phthalate, dioctyl phthalate, phthalic anhydrice, dioxane, i-propylcther, benzoyl peroxide, propylene oxide, benzaldehyde. lnaphthaldehyde, cyclohexanone, tetraphenyl hydrazine, dimethyl triphenyltrimethoxytrisiloxane, bisphenolepichlorohydrin-derived ether-cpoxidc epoxide resin, ethyl acetate, polyvinyl methyl ether, octyl diphenyl phosphate, phthalic anhydride, acetyl acetone, dimethyl formamide. propionaldehyde, l-nitropropane and acetaldehyde. 

1. A PROCESS FOR PRODUCTION OF A HIGHLY REACTIVE PYROPHORIC ALUMINUM WHICH PERMITS CREATION AND MAINTENANCE OF NASCENT ALUMINUM SURFACES WHILE INHIBITING REWELDING TOGETHER OF SUCH SURFACES WHICH COMPRISES MILLING PARTICULATE ALUMINUM IN THE PRESENCE OF A MILLING AID CAPABLE OF SORBING ONTO THE SURFACE OF THE ALUMINUM SUFFICIENTLY TO PREVENT WELDING OF THE PARTICLES AND AT THE SAME TIME ALLOW ACCESS BY A RWACTIVE SUBSTANCE TP THE NASCENT ALUMINUM SURFACE; SAID MILLING AID BEING SELECTED FROM THE GROUP CONSISTING OF: OXYGEN-CONTAINING COMPOUNDS, OLEFINS, HYDROCARBON FREE RADICALS, HYDRAZINE FREE RADICALS, AND CHLORINATED HYDROCARBONS.
 2. The process of claim 1 wherein the particulate aluminum comprises atomized aluminum powder.
 3. The process of claim 1 wherein the milling aid is selected from the group consisting of ketones, aldehydes, amides, carboxylic acids, peroxides, epoxies, ethers, esters, organic phosphates, organic nitrates, organic sulfonates, silicones and anhydrides.
 4. The process of claim 1 wherein the milling aid is a highly sorptive oxygen-containing compound having insufficient reactivity to react to produce an undesirable compound in bulk during milling.
 5. The process of claim 1 wherein the milling is in the presence of an inert hydrocarbon.
 6. The process of claim 5 wherein the inert hydrocarbon is selected from the group consisting of hexane kerosene, mineral spirits and benzene.
 7. A dispersion adapted for activating particulate aluminum during milling same to permit creation and maintenance of nascent aluminum surfaces while inhibiting welding together of such surfaces, said dispersion comprising: a. particulate aluminum, b. a milling aid capable of sorbing onto the surface of the aluminum sufficiently to prevent welding of the particles and at the same time allow assess by a reactive substance to the nascent aluminum surface selected from the group consisting of oxygen-containing compounds, olefins, hydrocarbon free radicals, hydrazine free rAdicals, and chlorinated hydrocarbons, and c. an inert hydrocarbon.
 8. The dispersion of claim 7 wherein the particulate aluminum comprises atomized aluminum powder.
 9. The dispersion of claim 7 wherein the milling aid is selected from the group consisting of ketones, aldehydes, amides, carboxylic acids, peroxides, epoxies, ethers, esters, organic phosphates, organic nitrates, organic sulfonates, silicones and anhydrides.
 10. The dispersion of claim 7 wherein the milling aid is a highly sorptive oxygen-containing compound of limited reactivity to stabilize the surface without preventing access to the nascent aluminum after completion of the milling.
 11. A process for improving the reactivity of aluminum which comprises milling particles of atomized aluminum in the presence of an inert hydrocarbon and at least one sorptive-type milling aid selected from the group consisting of ketones, amides, aldehydes, carboxylic acids, peroxides, epoxies, esters, organic phosphates, organic nitrates, organic sulfonates, silicones, anhydrides, olefins, hydrocarbon free radicals, hydrazine free radicals, and chlorinated hydrocarbons, thereby sorbing said milling aid on the surface of said particles to promote the reactivity thereof.
 12. A process for creating and maintaining nascent surfaces on particulate aluminum which comprises attacking freshly generated nascent surfaces of particles of aluminum with oxygen portions of oxygen-containing organic molecules during milling said aluminum, thereby stabilizing said surfaces to a controlled reactivity sufficient to prevent welding of the particles.
 13. The process of claim 12 wherein the surfaces of the particles of aluminum are stabilized sufficiently to make them reactive with hydrogen and an olefin to form an aluminum alkyl compound.
 14. A process for activating aluminum powder which comprises milling particulate aluminum in the presence of a milling aid capable of sorbing onto the surface of the aluminum sufficiently to stabilize it and at the same time allow access by a reactive substance to the nascent aluminum surface, said milling aid comprising at least one substance selected from the group consisting of methyl ethyl ketone, benzophenone, dimethyl phthalate, dioctyl phthalate, phthalic anhydride, dioxane, i-propylether, benzoyl peroxide, propylene oxide, benzaldehyde, 1-naphthaldehyde, cyclohexanone, tetraphenyl hydrazine, dimethyl triphenyltrimethoxytrisiloxane, bisphenolepichlorohydrin-derived ether-epoxide epoxide resin, ethyl actate, polyvinyl methyl ether, octyl diphenyl phosphate, phthalic anhydride, acetyl acetone, dimethyl formamide, propionaldehyde, 1-nitropropane, acetaldehyde, 2-hexene, aluminum chloride, triethyl aluminum ethylene, isoprene, hexaphenylethane and carbon tetrachloride.
 15. A process for activating particulate aluminum which comprises attacking freshly generated surfaces of particles of aluminum with oxygen portions of oxygen-containing organic molecules during milling said aluminum, thereby stabilizing said surfaces to a controlled reactivity, said oxygen-containing organic molecules being provided in methyl ethyl ketone.
 16. A process for activating particulate aluminum which comprises attacking freshly generated surfaces of particles of aluminum with oxygen portions of oxygen-containing organic molecules during milling said aluminum, thereby stabilizing said surfaces to controlled reactivity, said oxygen-containing organic molecules being provided in at least one substance selected from the group consisting of methyl ethyl ketone, benzophenone, dimethyl phthalate, dioctyl phthalate, phthalic anhydrice, dioxane, i-propylether, benzoyl peroxide, propylene oxide, benzaldehyde, 1-naphthaldehyde, cyclohexanone, tetraphenyl hydrazine, dimethyl triphenyltrimethoxytrisiloxane, bisphenolepichlorohydrin-derived ether-epoxide epoxide resin, ethyl acetate, polyvinyl methyl ether, octyl diphenyl phosphate, phthalic anhydride, acetyl acetone, dimethyl formamidE, propionaldehyde, 1-nitropropane and acetaldehyde. 